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Re: maphash

From: Stephen J. Turnbull
Subject: Re: maphash
Date: Thu, 24 Apr 2003 16:46:33 +0900
User-agent: Gnus/5.090016 (Oort Gnus v0.16) XEmacs/21.5 (cabbage)

>>>>> "rms" == Richard Stallman <address@hidden> writes:

    I have discovered by experimentation that maphash actually does what 
    I hoped it would, which is to pass key/value pairs to the mapping 
    function in the same order in which they were added to the table. 

    rms> An small anount of experimentation doesn't show you it will
    rms> always to do that.  It would be necessary to study the code
    rms> and construct a proof, before we could promise this to the
    rms> users.

If I understand the OP's description correctly, I can already promise
you that code depending on such a feature won't be portable to XEmacs:

(let ((my-hash (make-hash-table))
  (puthash "key1" "val1" my-hash)
  (puthash "key2" "val2" my-hash)
  (puthash "key3" "val3" my-hash)
  (maphash (lambda (k v) (setq result (cons k result))) my-hash)
  (reverse result))

=> ("key2" "key3" "key1")

Institute of Policy and Planning Sciences     http://turnbull.sk.tsukuba.ac.jp
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